A RECENT report (Cooper,101953) has indicated that ligation of the anterior choroidal artery in patients with paralysis agitans may ameliorate the tremor and rigidity associated with this syndrome and permit greater range of voluntary movement. Precisely why ligation of this vessel has been associated with these beneficial effects has not been answered, but it has been postulated that they probably are the result of localized ischemia and/or necrosis of portions of the globus pallidus. It has previously been determined (Carpenter, Whittier, and Mettler,91950) that localized stereotaxic lesions of the globus pallidus can ameliorate or abolish choreoid hyperkinesia in the Rhesus monkey resulting from localized lesions of the subthalamic nucleus of Luys. However, bilateral simultaneous lesions in the monkey which destroyed approximately 10% of the pallidum on each side have not been compatible with survival. It is claimed by Spiegel and Wycis* that patients with paralysis agitans